Unless the engine check light is on your problem must be service related.With my clients who come into my network with vehicle as you described I generally ask the following questions;-when last was the intake,throttle body and injectors properly cleaned.In case of injectors removed and serviced.-when last were spark plugs changed and if so with what.-Has the vehicle suffer any overheating or associated trauma.-How regularly is the oil and filter changed and with what products.Most times I have found that the average owner demonstrates a loose maintenance regime and does not for instance do a full "baseline" service every 18 to 24 months using proper consumerables.A full service which is designed to baseline the vehicle will normally manifest a 'poppin' in the performance of the vehicle and is quite unmistakeable to the owner.

@toyolink... The only thing I haven't done from the list of stuff you called out was clean the injectors. However... Prior to my homemade cai attempt the car would reach 200kmph quite easily... It was only since I tried out the cai that this issue came about and now the car won't go past 140...

I was told to have the diagnostics run on the engine and possibly reset the brain from the scanner itself and see if this resolves the problem. NB The check engine light is NOT on...

I am completely at a lost with this thing but many thanks for your input...